<html>
    <body>
        <h3>1+1 = {{ 1+1 }}</h3>
        <h3>book_name变量：{{ book_name }}</h3>
        <h3>book_name首字母大写：{{ book_name|capitalize }}</h3>
        <h3>book_name小写：{{ book_name|lower }}</h3>
        <h3>book_name大写：{{ book_name|upper }}</h3>
        <h3>所有单词首字母大写：{{ message[0]|title }}</h3>
        <h3>去除前后空格：{{ message[1]|trim }}</h3>
        <h3>去除html标签前：{{ message[2]}}</h3>
        <h3>去除html标签：{{ message[2]|striptags }}</h3>
        <h3>字符串不转义：{{ message[2]|safe }}</h3>
    </body>
</html>
